August 25, 2010

 

Genetic test breakthrough identifies IPN virus in salmon

 

 

The Norwegian company Aqua Gen has developed a new genetic test that quickly determines which salmon have the highest resistance to the IPN virus.

 

The recently launched commercial product could mean a breakthrough in the battle against this costly disease.

 

In 2007, researchers at the Norwegian companies Aqua Gen and Nofima Marin and at the Centre for Integrative Genetics (CIGENE) discovered the markers for a gene that makes salmon more resistant to the virus causing infectious pancreatic necrosis (IPN).

 

The new knowledge about these markers is now being applied to selective breeding-and Aqua Gen is already supplying QTL eggs from parent fish genetically-screened for IPN resistance.

 

There are often multiple genes that play a role in determining an individual's susceptibility to a certain disease. However, in this case, the researchers were very surprised to discover that a single gene largely accounts for the genetic variation in salmon resistance to the IPN virus.

 

According to Aqua Gen molecular geneticist and project manager Thomas Moen, the gene explains 80% of the variation in resistance to IPN in salmon.

 

Discovering such a gene enables scientists to select for broodstock with the highest probability of producing offspring that are protected from the IPN virus. The test requires only a blood or tissue sample to indicate the most resistant fish to select.

 

Specialised QTL eggs are from parent fish that have tested positive for certain genetic markers so that their offspring inherit a high resistance to IPN. The product, launched in European markets starting in November 2009, could spell good business for Aqua Gen and the industry at large. Aqua Gen is achieving added value of 30-40% on the market compared to conventional products not genetically tested.

 

The method will also advance animal welfare in the aquaculture industry; IPN currently accounts for much of the mortality among production fish stocks, particularly in the early production phases.

 

Furthermore, genetic testing to select for higher disease resistance will replace conventional challenge testing. In a conventional selective breeding programme, some 80,000-100,000 fish in each generation would have to be exposed to the virus.

 

The researchers are still not certain as to exactly which gene it is that gives salmon their immunity to the IPN virus. But this knowledge is also right around the corner.

 

Efforts to sequence the salmon genome are in full swing now. The sequencing project is a collaborative effort between Canada, Norway and Chile.

 

Norway is providing nearly 40% of the funding through a joint investment by the Norwegian industry and the public funding instruments. An important driving force behind the sequencing is the need to make salmon more resistant to diseases.